Lexicon before and after epilepsy surgery in adolescents

Objective: Poor performance on confrontation naming tasks by children and adolescents with pharmacologically intractable epilepsy has been interpreted as indicating impairments of lexicon, that is, the store of words in long-term memory. However, confrontation naming performance crucially depends not only on word knowledge but also on other functions such as fluency. We applied an alternative method to assess lexicon with the aim of tracing deficits in lexicon before and after surgery in adolescents with pharmacologically intractable epilepsy. Method: Sixteen patients and 32 age- and sex-matched controls completed the Dutch version of the controlled oral word production task. Responses were used to calculate indices of lexical fluency (retrieval efficiency), lexical breadth (vocabulary size), and lexical depth (knowledge of word properties), as well as use of search strategies. Results: Adolescents with pharmacologically intractable epilepsy had lower lexical fluency scores than healthy peers, but did not differ from them on the dimensions of lexical breadth and lexical depth. Patients demonstrated reduced use of search strategies. In fact, the difference in lexical fluency between patients and controls disappeared after controlling for Full Scale IQ (obtained using the Dutch version of the 3rd edition of the Wechsler Intelligence Scale for Children (WISC-IIINL; Kort et al., 2005; Wechsler, 2002) or-for older children-the Dutch version of the first edition of the Kaufman Adult and Adolescent Intelligence Test (KAIT; Kaufman & Kaufman, 1993; Mulder, Dekker, & Dekker, 2004) and use of search strategies. In patients, changes in the use of the antiepileptic drug carbamazepine were associated with lexical fluency. Conclusion: Adolescents with pharmacologically intractable epilepsy differ from their healthy peers mainly in lexical fluency, rather than word knowledge per se. (PsycINFO Database Record